GnuPlot in your toolset

06 Jul 2017 in gnuplot

Recently I was asked to investigate a web server issue not responding in regural intervals.

After spending some time digging around in logs and configs, I developed a solution to log the server load at small time intervals in order to have a better view of what's happening.

To do this, create a very simple shell script to store the time and server load:

echo date +%Y%m%d-%H%M%S >> report/uptime.log
uptime >> uptime.log

Then run this script at an interval of 5 secs:

while true; do echo -en . ; bash ; sleep 5; done

When enough data has gathered, prepare for use with gnuplot:

cat uptime.log \
    | sed 'N;s/\n/ /' \
    | cut -d' ' -f1,15 \
    | sed -s 's/,//g' > uptime.plot

And plot it:

gnuplot -p -e '
    set xdata time;
    set timefmt "%Y%m%d-%H%M%S";
    plot "uptime.plot" using 1:2;